Method of preparing uranium tetrachloride



Patented Sept. 7, 1954 METHOD OF PREPARING URANIUM TETRACHLORIDE Edward L. Wagner, Providence, It. I., and Laurence B. Dean, Columbus, Ohio, assignors, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission N Drawing. Application May 4, 1949, Serial No. 91,425

8 Claims.

This invention relates to uranium compounds and more particularly it is concerned with the preparation of uranium tetrachloride from compounds of uranium.

The method of preparing uranium tetrachloride most widely used before this invention was to react an oxide of uranium with carbon tetrachloride vapor. In order to carry out this reaction at a reasonable rate it has been found necessary to employ a reaction temperature of the order of 450 C. At this temperature appreciable amounts of uranium oxide are converted to uranium pentachloride with consequent loss of product. A further disadvantage of this process arises through the formation of appreciable amounts of phosgene and its dissociation products. These compounds are diflicult to handle and extremely dangerous to operating personnel. Moreover, for the sake of economy it is desirable to employ a process which can be carried out at as low a temperature as possible.

Accordingly, one object of this invention is to provide a method for preparing substantially pure uranium tetrachloride with a high yield.

Another object of the invention is to provide a method for producing uranium tetrachloride with a high yield at a lower temperature than has heretofore been possible.

A further object is to provide a method of converting an oxide of uranium to uranium tetrachloride without producing appreciable quantities of uranium pentachloride.

Other objects will be in part obvious and in part pointed out hereinafter.

In accordance with the present invention the foregoing objects are accomplished, generally speaking, by reacting an oxide of uranium with hexachlorpropylene vapor. In general, the starting material may be any uranium compound converted, for example by calcination, to an oxide. For example, such compounds as uranyl nitrate and other uranyl salts, (NH4) 2U4O7, etc. are first calcined to oxide and then reacted in accordance with this invention. The oxides of uranium which are preferably used in this process are U03 (uranium trioxide) and U308 (uranous uranic oxide) and especially the former.

The reaction proceeds easily at a temperature of about 350 C. with substantially no formation of the pentachloride. Temperatures as high as 450 may be employed to increase the speed of the reaction without increasing appreciably the amount of the pentachloride formed. Similarly, while the reaction is carried out without difliculty at substantially atmospheric pressure, super-atmospheric pressure may be employed to increase the speed of reaction.

The following description of the preferred method of carrying out this invention is presented here with the understanding that the invention should not be limited to the specific details disclosed therein.

Uranium trioxide is charged into the heated reaction zone of a furnace. The inlet to the furnace communicates with a boiler for the hexachlorpropylene and a source of an inert gas While the furnace outlet is provided with a condenser. Initially the trioxide is heated in an inert atmosphere until the temperature in the reaction zone rises to about 300 C. Thereafter a slow stream of hexachlorpropylene vapor is flowed through the heated portion while the temperature is increased to about 350 C'. After the temperature reaches this value, the rate at which the hexachlorpropylene vapor is distilled through the reaction zone is increased and the temperature is maintained at 350 C. The reaction is generally completed in 3 to 4 hours or after the passage through the reaction zone of about 20 moles of hexachlorpropylene to 1 mole of the trioxide. The unreacted hexachlorpropylene is recovered from the condenser and may be reused or recirculated.

At the conclusion of the reaction the uranium tetrachloride is cooled in an inert atmosphere which should be as dry as possible since the salt is hygroscopic.

In the method just described the product formed is substantially completely chlorinated and reduced to crystalline uranium tetrachloride with a yield of upwards of since virtually no uranium pentachloride is formed. At temperatures of 450 and higher the amount of the pentachloride formed is increased and moreover there is also a tendency toward decomposition of the hexachlorpropylene. The average crystal size of the product is also affected by temperature, increasing as the temperature is increased. The reaction does take place at temperatures as low as 300 C. but at a relatively slow rate.

The proportions of hexachlorp-ropylene to the uranium oxide may vary considerably with around 3.0 to 3.5 moles of the hexachlorpropylene used for each mole of uranium trioxide. At least this amount should be employed and, as is usual in reactions between vapor and solid where the vapor is flowed continuously over the solid, a considerable excess of the vapor should be brought into contact with the solid even though only a small part of the vapor actually enters the reaction.

Other alternatives will Hoe apparent to those skilled in the art.

Since many embodiments might be made of the present invention and since many changes might be made in the embodiment described, it is to be understood that the foregoing description is to be interpreted as illustrative only and not in a limiting sense.

We claim:

1. A method of preparing uranium tetrachloride which comprises heating a uranium oxide whose atomic ratio of oxygen to uranium is greater than two in an atmosphere composed essentially of the vapor of hexachlorpropylene at a temperature in excess of 300 C.

2. A method of preparing uranium tetrachloride which comprises heating an oxide of uranium wherein the atomic ratio of oxygen to uranium is greater than two in an atmosphere of hexachlor propylene vapor at a temperature of at least 300 C.

3. A method of preparing uranium tetrachloride which comprises heating an oxide of uranium wherein the atomic ratio of oxygen to uranium is greater than two in an atmosphere composed essentially of the vapor of hexachlorpropylene at a temperature in the range 350 to 450 C.

4. A method of preparing uranium tetrachloride which comprises heating an oxide of uranium selected from the group consisting of U03 and U303 in an atmosphere composed essentially of the vapor of hexachlorpropylene at a temperature in excess of 300 C.

5. A method of converting an uranium oxide whose atomic ratio of oxygen to uranium is greater than two to uranium tetrachloride which comprises continuously passing the vapor of hexachlorpropylene alone over said oxide at a temperature of 350 C. for at least 3 hours.

6. A method for preparing uranium tetrachloride which comprises heating uranium trioxide in an atmosphere composed essentially of the vapor or" hexachlorpropylene at a temperature in excess of 300 C.

'7. A method of preparing uranium tetrachloride which comprises heating uranium trioxide in an atmosphere composed essentially of the vapor of hexachlorpropylene at a temperature in the range 350 to 450 C.

8. A method of preparing uranium tetrachloride which comprises heating uranium trioxide in an inert atmosphere to a temperature of 300 C., passing the vapor of hexa'chlorpropylene alone over said trioxide while increasing the temperature to 350 C., thereafter continuing the passage of the hexachlorpropylene vapor over said trioxide to produce uranium tetrachloride and cooling the uranium tetrachloride in an inert atmosphere.

References Cited in the file of this patent Roscoe, Journal of the Chemical Society, New Series, vol. 12, pages 933-935 (1874). (Copy in Scientific Library.)

Camboulives, Comptes Rendus, vol. 150, pages 175-177 (1910). (Copy in Scientific Library.)

Mellor, Inorganic and Theoretical Chemistry, vol. 12, page (1932) Published by Longmans, Green and Company, London. (Copy in Division 59.) 

1. A METHOD OF PREPARING URANIUM TETRACHLORIDE WHICH COMPRISES HEATING A URANIUM OXIDE WHOSE ATOMIC RATION OF OXYGEN TO URANIUM IS GREATER THAN TWO IN AN ATMOSPHERE COMPOSED ESSENTIALLY OF THE VAPOR OF HEXACHLORPROPYLENE AT A TEMPERATURE IN EXCESS OF 300* C. 